Petrolene composition containing atactic polyolefin



United States Patent U.S. Cl. 26028.5 4 Claims ABSTRACT OF THEDISCLOSURE This invention is concerned with an asphaltene-freecomposition suitable for paving or similar uses comprising a majoramount of petrolene and a minor proportion of atactic polymers orcopolymers of C to C olefins. Such compositions have properties superiorto those compositions of asphalt and atactic polypropylene.

The present invention relates to petrolene, i.e. deasphaltened asphalt,compositions containing atactic polyolefin. In particular, it concernscompositions suitable for paving and other related uses of decreasedtemperature susceptibility and improved ductility and viscositycharacteristics, which compositions comprise a major proportion of apetrolene and a minor proportion of atactic polymers or copolymers of Cto C olefins.

Paving grade asphalts are made from residuum stocks derived from variouscrudes. In the past, one of two methods has been generally employed toproduce high quality asphalts suitable for road paving. One methodinvolves straight vacuum deduction, while the other method involves airblowing of pipe still residuum. Both these methods have significantdrawbacks. One of the major problems inherent in both these methods isthe difficulty. of meeting paving asphalt specifications prescribed bystate and federal governments. It is usually necessary to exercisecareful selection of crude and very careful control in said reduction orin said air blowing to meet these paving asphalt specifications, namely,in such properties as penetration, temperature susceptibility, viscosityand ductility.

Recently, it has been suggested in U.S. Patent 3,144,423 that pavinggrade asphalts which meet state and federal government specificationsmay be provided by adding small amounts of atactic polypropylene withasphalt, thus providing a simple method of meeting specifications. Theasphalt paving compositions described in U.S. 3,144,423 consist of amixture of asphalt and a small amount of atactic polypropylene. It hasnow been found and forms a basis of the present invention that superiorpaving compositions can be obtained by first deasphaltening an asphaltto make etrolenes and then incorporating a small amount of atacticpolypropylene or similar atactic polyolefin into the petrolenes.

Asphalt is a thermo plastic mixture of high molecular weighthydrocarbons plus a small amount of sulfur, nitrogen, and oxygenderivatives. Due to the complexity of the large number of hydrocarbonsin asphalt, the exact chemical identity has not been established toowell. However, a large portion of asphalt has been identified aspolycyclic aromatics, some being substituted with aliphatic side chains.Asphalt is considered to be a colloidal suspension in which very highmolecular weight hydrocarbons called asphaltenes are suspended in amatrix of lower molecular weight hydrocarbons called petrolenes. Thepetrolenes are soluble in a certain class of petroleum solvents whereasthe asphaltenes are insoluble in said solvents. Therefore, solventprecipitation can be used to separate asphaltenes and petrolenes.

Asphaltenes are solid infusible brown-black material having a specificgravity of about 1.15 to 1.25 at 77/77 F. and may be defined as thatportion of asphalt which is insoluble in petroleum solvents composedentirely of aliphatic open chain hydrocarbons, i.e. paraffinic solvents,having a gravity of 86 to 88 Baum being evuivalent to a specific gravityof 0.638 at 60/60 F.) and at least of whose constituents boil betweenand 150 F. Pure paraffinic solvents such as n-pentane, n-hexane,n-heptane and iso-octane accomplish essentially the same separation ofasphaltenes and petrolenes and have the advantage of uniformity ofsolvent composition.

Petrolenes may be defined as that portion of an asphalt, or crude oilresiduum, from which the asphaltenes have been removed. The process ofremoving the asphaltenes is termed deasphaltening and one such method isdescribed in U.S. Patent 3,087,887. Various other methods ofdeasphaltening are well known in the art.

The data in Table I illustrate the composition and properties of typicalasphaltenes and petrolenes.

According to the present invention, superior paving grade compositionsare prepared by blending petrolenes with atactic polyolefins.

Atactic, i.e. substantially non-crystalline or substantially amorphous,polyolefins suitable for use in the present invention may be made bypolymerization of ethylene, or propylene, or by copolymerization ofmixtures of ethylene and propylene. Although it is desirable insofar asis practical to employ polyolefins that are entirely atactic and devoidof crystalline structure, it is not always possible to secure suchpurities, particularly in commercial operations. Thus, for the purposeof the present invention the term atactic polyolefin includes, inaddition to polyolefins which are entirely atactic, polyolefins whichare substantially non-crystalline, i.e. polyolefins which contain nomore than about 20 wt. percent, preferably less than 10 wt. percent,crystalline polymer. Crystalline polymer is that polymer which isinsoluble in normal heptane when subjected to Soxhlet extraction for 24hours. The molecular weight of the atactic polyolefin can vary dependingupon the particular polymer or copolymer employed but in general willrange from about 10,000 to about 200,000 and is preferably about 10,000to about 100,000, and most preferably about 25,000 to 60,000. Themolecular weight ranges are based upon viscosity weight average datausing the Kinsinger correlation as determined at a temperature of C. anda concentration ratio of 1 mg. polymer/1 ml. of Decalin. Atacticpolypropylene is preferred.

An inexpensive source of atactic polyproplene is the xylene slurry ofreject or off specification polypropylene from a commercialpolymerization process using a metal alkyl-metal halide catalyst system,the so called Ziegler type of catalyst. The slurry is freed from itsxylene by distillation to give a dry mixture of both atactic andisotactic polypropylene. To this dry mixture is added any suitablealiphatic hydrocarbon solvent or mixture of aliphatic hydrocarbons, forexample, a C to C naphtha cut, or normal heptane, or normal hexane.These solvents selectively dissolve out the atactic polypropylene whileleaving the bulk of the crystalline polypropylene in the insolublestate, yielding a solution, which after filtering out the insolublecrystalline polypropylene can be blended with the above-describedpetrolenes. On the other hand,

if a solution blending method is not desired all of the aliphatichydrocarbon solvent can be removed, for example by simple heating,leaving atactic polypropylene.

In another method for isolating atactic polypropylene from rejectpolypropylene of a commercial polypropylene plant the xylene filtratestream may be blended directly, with or without a partial removal ofsome of the xylene, with the above-described petrolenes. The xylenefiltrate stream may constitute xylene and about 2 to 50 wt. percenttotal polypropylene of which up to about 40 wt. percent of thepolypropylene is in the isotactic (i.e. crystalline) form. After thesolution blending has been completed, the mixture is passed through aheater under pressure and flash evaporated under vacuum to remove someor all of the xylene.

The amount of atactic polyolefin, preferably atactic polypropylene,which is mixed with the petrolene may vary depending upon the finalproperties to be achieved in the paving composition. In general, thecomposition of the present invention will comprise a major amount ofpetrolenes and about 1 to 30 wt. percent, preferably about 3 to 20 wt.percent, atactic polyolefin. The composition will be substantiallyasphaltene-free, i.e. containing less than 1.0 wt. percent andpreferably less than 0.5 wt. percent asphaltene. All of said weightpercents are based upon the weight of the total composition. In a mostpreferred composition about 3 to 20 wt. percent atactic polypropylene isincorporated into the petrolenes.

Obvious modifications such as blending of the asphalt composition of theinvention with mineral aggregates, cement, sand, asbestos, vermiculite,Fiberglas and the like are included in the scope of this invention.

The composition of the present invention can be prepared by simplefluxing (i.e., simple mixing) of the atactic polyolefin and thepetrolenes. In general, temperatures in the range of about 200 F. toabout 450 F. are suitable.

Some of the improvements attained by combining atactic polyolefin,particularly atactic polypropylene, with petrolene are illlustrated bythe following examples. In the examples the physical property data shownwere obtained by the procedures indicated below:

Softening point was determined by the ring and ball method provided byASTM D3662T. Penetration was determined by the procedure of ASTM D561.Penetration ratio was calculated by multiplying by 100, the ratio of thepenetration at 39.2 F. to the penetration at 77 F. Ductility wasdetermined by the procedure of ASTM D11344. Thin film test residue wasdetermined by the procedure of ASTM D1754-63T. Aging index wasdetermined by the procedure described in ASTM STP No. 309, p. 133(1961). Viscosities were determined by the Furol viscosity procedure andby the micro method for determining viscosity Which is described in theProcedings of typical properties shown above in Table I. The atacticpolypropylene employed was recovered from the xylene slurry of rejectpolypropylene (mixture of atactic and crystalline) from a commercialpolypropylene plant. The reject polymer was dried (i.e., freed fromxylene) and extracted with normal heptane. The normal heptaneselectively dissolved the atactic polypropylene while leaving thecrystalline polypropylene in the insoluble state. The resulting solutionwas filtered to remove insoluble crystalline polypropylene and then-heptane was evaporated to yield water white atactic polypropylenehaving a molecular weight of about 39,500, an intrinsic viscosity of.533 at 135 C., a density of .861, a crystalline polymer content of 8.9wt. percent (infrared), and insolubles (in n-heptane) content of 2.9 wt.percent. The physical properties of the resulting pavings compositionswere compared with the physical properties of the straight reducedasphalt from which the petrolene was derived. The results are shown inTable II.

TABLE II Composition (wt. percent):

Straight reduced asphalt 100 Petrolene 80 Ataetie polypropylene 20Properties:

Softening point, F 112 170 Penetration at 77 F. (100 gins/5 185 158Penetration at 39 sec.) 60 97 Pen-ratio 30. 2 52. 5 Ductility at 392 F.(1 cm./min.). 50+ Furol vis. at 275 F. SFS 116 530 The results in TableII illustrate how temperature susceptibility as measured bypenetration-ratio and Furol viscosity at 275 F., of an asphalt can begreatly improved by deasphaltening said asphalt and adding atacticpolypropylene.

EXAMPLE 2 Asphalt Petrolene Softening point, F 112 111 Penetration at392 F. (200 gins/ see.) 38 40 Penetration at 77 F. (100 gms./5 see)...108 112 Ductility at 392 F. (5 cmJmin.) 50+ 50+ Furol vis. at 275 F.,SFS 160 171 TABLE IIL-COMPARISON OF ASPHALT VERSUS PETROLENE IN ATACTICPOLYPROPYLENE COMPOSITIONS Composition, percent by wt. Thin film testresidue Atactic poly- Pen. at 77, Vise. at 77. Percent Visc. at 77,Aging Asphalt Petroleno propylene 100 g./5 see. poise 10 ret. pen. poi5e10 index 5 74 2 50 71 6. 70 2. 74 5 74 1. 52 84 2. 80 1. 78 3 81 1. 8564 5.02 2. 85 3 81 1. 51 76 2. 45 1. 63

the Association of Alphalt Paving Technologists, 24, 31 The data inTable III establish a superiority of petrolene- EXAMPLE 1 A pavingcomposition of improved physical properties was prepared by blending =80wt. percent petrolenes with 20 wt. percent atactic polypropylene bysimple mixing at about 250 F. The petrolene was that portion of astraight reduced asphalt from a Lagunillas crude which remained aftersaid asphalt was deasphaltened (using n-hexane in a atacticpolypropylene compositions over asphalt-atactic polypropylenecompositions. For example, comparing compositions A and B, which havethe same penetration at 77 F., it was unexpectedly found in the ThinFilm Test that the percentage of retained penetration was notablyhigher, indicating less hardening in the case of the petrolene-atacticpolypropylene blend, i.e., composition B. This superior resistance tohardening is also shown by the lower Aging Index. Compositions C and Dprovide a one-stage extraction at 77 B). These petrolenes had thecomparison, again at the same penetration levels, and,

again, the results show the superiority of the petroleneatacticpolypropylene blend as compared to the asphaltatactic polypropyleneblend.

Table IV shows the penetration and ductility characteristics of blendsF, G, H and J.

The data in Table IV was used to compare the ductility of apetrolene-atactic polypropylene composition of 50 penetration at atemperature of 39.2 F. with the ductility of an asphalt-atacticpolypropylene composition of 50 penetration also at a temperature of 392F. Based upon this data at 50 penetration and at 392 F. the petrolenecomposition would have a ductility of 74 cm. while the asphaltcomposition'would have a ductility of 15 cm. Thus, it is apparent thatthe petrolene compositions of the present invention possess superiorductility as compared to compositions employing asphalt.

While the invention has been described primarily with reference tocompositions for use in paving, the compositions of the presentinvention may find equal utility where compositions having similarphysical properties are required. For example, soil stabilization andprotection of banks and canals by coating, pipe coating, coating ofmetals which are to be buried in soil and molding articles such asbattery boxes and tiles, and the like, are all contemplated.

What is claimed is:

1. A substantially asphaltene-free composition suitable for use as apaving or coating composition comprising a major amount of petrolene andabout 1 to 30 wt. percent, based on the total composition, atacticpolymer of C to C monoolefin.

2. A substantially asphaltene-free composition comprising a major amountof petrolene and about 1 to 30 wt. percent atactic polypropylene.

3. A substantially asphaltene-free composition according to claim 2wherein the molecular weight of said atactic polypropylene is in therange of about 25,000 to 60,000.

4. A composition comprising a major amount of petrolene and about 3 to20 wt. percent atactic polypropylene, said composition beingsubstantially asphaltene-free.

US. Cl. X.R.

